Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.89	10.298%	$174.1495	$174.15	$174.15	$174.10
Purchase #2	$94.70	11.431%	$105.5252	$105.53	$105.55	$105.50
Purchase #3	$51.90	10.867%	$57.54	$57.54	$57.55	$57.50
Purchase #4	$88.41	10.137%	$97.3721	$97.37	$97.35	$97.40
Purchase #5	$90.66	13.273%	$102.6933	$102.69	$102.70	$102.70
Purchase #6	$138.47	13.241%	$156.8048	$156.80	$156.80	$156.80
Purchase #7	$154.55	6.612%	$164.7688	$164.77	$164.75	$164.80
7 purchase totals =	$776.58		$858.8537	$858.85	$858.85	$858.80